Honing machine



Dec. 30, 1941. w. M. FAIRBAIRN HONING MACHINE Filed Aug. 9. 1939 2Sheets-Shedl l uw j @mm:

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HONING MACHINE Filed Aug. 9, 1939 2 Sheets-Sheet 2 CCEJF@ Wa//er'S70/)607797 TTO @Sys Patented Dec. 30, 1941 HONING MACHINE Walter M.Fairbairn, Rockford, Ill., assignor to Barnes Drill Co., Rockford, Ill.,a corporation of Illinois Application August 9, 1939, Serial No. 289,193

13 Claims.

The invention relates to machines for dressing cylindrical surfaces by ahoning or lapping operation and more particularly to honing or lappingmachines of the horizontal type.

One object of the invention is to provide a machine of the above generalcharacter which is of simple compact construction, which can bemanufactured at relatively low cost, and which lends itself readily toquantity production.

Another object of the invention is to provide an improved reciprocatoryhead for horizontal honing or lapping machines which embodies in oneunitary structure, all of the driving and control instrumentalitiesrequired for operating the machine including means for reciprocating thehead, means for rotating the tool spindle continuously, means forindexing the tool spindle, and means for expanding and contracting thetool.

A further object is to provide improved drive mechanism forreciprocating the tool head or carriage of a horizontal honing machineor the like.

Other objects and advantages of the invention will become apparent fromthe following detailed description of the preferred embodimentillustrated in the accompanying drawings in which:

Figure 1 is a side elevational view of a horizontal honing and lappingmachine embodying the features of the invention.

Fig. 2 is a vertical sectional view taken longitudinally of thereciprocatory head showing details of the spindle driving and headreciprocating mechanisms.

Fig. 3 is a transverse sectional view of the machine taken along theline 3--3 of Fig. 2.

Fig. 4 is a schematic diagram of the hydraulic and electrical circuitsshowing the arrangement and relationship of the various operating andcontrol devices of the machine.

By way of illustration, the invention has been shown and will bedescribed hereinafter as em- .bodied in a single spindle honing andlapping to illustrate the invention comprises generally an elongatedframe or base consisting of a main section 5 and an outboard section 6bolted or otherwise rigidly secured together in end-to-end relation. Thelatter section constitutes a work support and is desirably equipped withsuitable fixtures 1 for holding a work piece W, such as an elongatedhollow tube or cylinder.

'Ihe honing and lapping operations are performed with an expansible andcontractible cylindrical abrasive tool or hone T which may be of anysuitable or well known construction. As these operations require arelative reciprocation of the tool and the work piece to traverse thetool from one end of the work piece to the other, and a simultaneousrelative rotation of the tool and work piece, the tool T, in thisinstance, is carried at one end of an elongated tubular driver 8 whichconstitutes an extension of a rotary spindle 9 journaled on areciprocatory head or carriage Ill. s herein shown, the head issupported for reciprocation by rollers I l (Figs. 2 and 3) journaled onthe head and operating on a guideway formed by spaced parallel channelmembers l2 (Fig. 3) mounted in inwardly facing relation on the sidewalls of the main base section 5.

The construction of the head is an important factor in the attainment ofthe objects of the present invention. Preferably, it is constructed inthe form of a' self-contained unit,that is, it has incorporated in oneunitary structure, all

of the power actuated instrumentalities for effecting the necessaryrelative movements of the tool and work. These include the driving andcontrol means for reciprocating the head I0, driviing means for rotatingthe tool spindle 9 either continuously or intermittently, and poweractuated means for expanding and contracting the tool T. Since thedriving means are all incorporated in the unitary head structure, asingle prime mover may be utilized to furnish power.

simplied since no provision is required for driving or controlmechanisms thus facilitating manufacture of this portion of the machine.

Refen'lng more particularly to Figs. 2 and 3. the head I9 preferablycomprises a housing built up of light weight metal castings assembled toform a hollow casing I5 for the driving and control mechanisms.Laterally projecting stud shafts I6 anchored in opposite side walls ofthe housing constitute axles for the rollers II which support the headon the guideway. The tool spindle 9 is supported at the forward end ofthe housing by front and rear bearings I 1 and I8, preferably of theanti-friction type. As herein shown the front bearing I1 is mounted in asuitable bore I9 in the end wall of the housing, while the rear bearingI8 is carried on a web or cross member extending transversely across thehousing. A' cap 2|" apertured for the reception of the spindle, isbolted to the housing to close the outer end of the bore I9 and to formwith the web 20 a closed chamber which may be filled with oil or otherlubricant for lubricating the spindle bearings.

Preferably a single prime mover, herein shown as an electric motor M, isemployed for driving the spindle, reciprocating the head, and expandingand contracting the tool. Current is supplied to the motor through a setof brushes B carried on a bracket 2Il depending from the head, thebrushes engaging elongated contact strips C connected with a suitablesource of current.

To provide a high degree of flexibility in adjusting the machine foroperating on various types of work, the drive for the spindle and thehead is preferably taken through a hydraulic variable speed transmissiondesignated generally by the reference character 22. This transmissionmay be of any suitable construction, but is preferably of the unit typesuch as the transmission manufactured by Vickers Inc. of Detroit,Michigan.

A hydraulic speed transmission unit oi.' the above character ordinarilyincludes a reversible rotary pressure fluid motor 23 (Fig. 4) and avariable delivery pump 24 for supplying pressure fluid to the motor. Inthe unitary type device the pump and motor are enclosed in a generallyrectangular casing 29 (Fig. 2) .which forms a sump or reservoir R inwhich surplus fluid for the pressure fluid system is stored. 'I'heconventional transmission unit has a constant speed input shaft 21projecting at one end and a variable speed output or drive shaft 28projecting at the other end. These shafts are the motor and pump shafts,respectively. A reversing valve V (Fig. 4) may be interposed between thepump and the motor to control the rotation of the latter. In theparticular unit shown by way of illustration, the valve V is of the wellknown pressure uid operated type and is arranged to be operated undercontrol of a pilot valve V-I also of well known construction.

In the exemplary machine the transmission unit 22 is mounted within thehousing I5 with the input shaft 21 projecting rearwardly therefrom. Themotor M is mounted on a bracket 29 projecting rearwardly from thehousing and is connected directly with the input shaft 21 by a suitablecoupling device 39. The drive shaft 28 is drivingly connected with themechanisms for rotating the tool spindle 9 continuously and forreciprocating the head respectively. These mechanisms in the presentinstance comprise suitable gear trains.

The mechanism for continuously rotating the tool spindle as shown inFig. 2 includes a gear 33 keyed to the inner end of the spindle 9 andarranged to mesh with a pinion 34 fast on an intermediate shaft 35rotatably supported in the housing I5 above and substantially parallelto the spindle. A gear 36 onthe intermediate shaft meshes with a pinion31 faston a shaft 38 which has a gear 39 meshing with the pinion 3| onthe drive shaft 28.

As it is desirable at times to interrupt the driving connection betweenthe drive shaft and the spindle, the gear 39 isloosely mounted on theshaft 38 and arranged to be drivingly connected thereto by a suitableclutch. The clutch as herein shown, comprises a sleeve member 40 splinedto the shaft 38 and provided on one face wtih suitable clutch teeth 4Iadapted to engage cooperating clutch teeth 42 formed on the hub of thegear 39. When the machine is to be used for honing, the clutch isengaged by shifting the member to its right hand position (as viewed inFig. 2) and the spindle is thus driven continuously. For lapping,however, the clutch member is shifted to 'the left-hand or disengagedposition, thereby interrupting the driving connection for the spindle sothat the spindle may be driven by the indexing mechanism to be describedhereinafter. A hand lever 43 (Fig. 1) accessible from the outside of thehousing is provided for shifting the clutch member 40 to engage ordisengage the clutch.

'I'he means for reciprocating the head, in its preferred form, comprisesa driving pinion 46 rotatably supported on the head and positioned tomesh with a stationary rack 41 mounted on the base section 5 below theguideway for the head.

,In order to eiectually eliminate backlash between the pinion and therack, the latter is split longitudinally into two sections arranged sideby side as shown in Fig. 3. 'Ihese sections are secured together as bybolts 48 threaded into upstanding lugs 49 formed on transverse webs 50welded or otherwise secured within the base section. The bolts 48project through elongated slots 5I in the respective rack sections sothat the sections may be shifted longitudinally one relative to theother to insure a tight engagement of the pinion and rack teeth.Compensation for wear of the coacting partsl can thus be readilyeffected and backlash in the reciprocating mechanism thus completelyeliminated.

As herein shown, the pinion 46 is keyed to a shaft 52 journaled in thelower part of the housing I5 and extending transversely across the same.The shaft 52, in this instance, is driven through the medium of a wormwheel 53 meshing with a worm 54 fast on a shaft 55 which in turn isdriven by a gear 56 meshing with the pinion 3| on the drive shaft. 'Ihehydraulic motor 23 is thus enabled to move the head along the guideway.

The direction of movement of the head on the guideway depends of courseupon the direction of rotation of the hydraulic motor 23. As aboveexplained, the direction of rotation of the motor is controlled by thereversing valve V which in turn is operated under control of the pilotvalve V-I. In order to effect reversal of the movements of the head atthe proper points in its reciprocatory stroke, that is. as the honingtool approaches the opposite ends of the Work piece,

means is provided for operating the pilot` valve.'

as an incident to the movement of the head. 'I'his means, as hereinshown, comprises a valve actuating member 51 (Figs. 3 and 4) in the formof a lever secured at one end to the movable member of the valve. Theother end of the member is arranged to' engage suitable limit stops 58and 59 supported on the machine base. The limit stops, as herein shown,are slidably supported on a rod 60 extending longitudinally of the basesection so that they may be adjusted to dene the desired limit positionsof the head at each end of its reciprocatory stroke. This adjustment ismade, of course, when the machine is initially set up for the particularwork piece to be honed` and the stops are then locked in set position inany suitable manner.

Since the spindle 9 is driven by the motor 23 through the medium of apositively acting transmission mechanism, the direction of rotation ofthe spindle is reversed each time the head reverses at the opposite endsof its .reclprocatory stroke. This is advantageous in equalizing thewear of the abrasive stones of the tool and it also reduces the tendencyof the stones to load with the material abraded from the work piece.

When the machine is to be used for performing a lapping operation, thatis, an operation in which the tool is 'rotated intermittently orindexed, the driving connection between the spindle and the transmissionunit 22 above described, is interrupted by disengaging the clutchelements 4I-42. The spindle is then drivingly connected with theindexing mechanism through the medium of a shiftable clutch member 6Ikeyed directly to the spindle.

The indexing mechanism, as herein shown, (Figs. 2 and 3) comprises apawl and ratchet device including a disk-'shaped driving member 1,62 anda sleeve-like driven member 63, both loosely mounted on the spindle 9between the front and rear bearings I1 and I8. A pawl 64 pivoted on theface of the driving member 62 is adapted to engage ratchet teeth 65 cutin the periphery of the. driven member 63 and thus provide a onewaydriving connection between the members whereby the driven member mayberotated in a counterclockwise direction (as viewed in Fig. 3) byappropriate movements of the driving member. The movements of thedriving member are imparted to the spindle through the clutch member 6I,these members having suitable clutch teeth in their adjacent facesadapted to be engaged upon. movement of the clutch member to theposition shown in Fig. 2. Upon movement of the clutch member to theright the clutch teeth are disengaged, thereby disconnecting the spindlefrom the index mechanism so that it may be connected with thetransmission unit by engagement of the clutch 4I-42 as above described.A hand lever 66 accessible from the outside of the housing is providedfor shifting the clutch member 6 I Suitable means is provided forimparting intermittent rotative movements to the driving member 62. Thismeans as herein shown is of the pressure uid operated type and includesa cylinder 61 (Fig. 3) mounted on the casing I5 with its axissubstantially perpendicular to the axis of the spindle. The cylinder istted with a working piston 68 having a piston rod 69 projecting into thehousing I5 in alinement with the drivi`ng member 62 of the pawl andratchet device. The piston rod is operatively connected with the drivingmember by means of rack teeth 10 cut therein adapted to mesh withsuitable` in one direction and then in the other. Such movements of themember in one direction are transmitted to the driven member 63 by thepawl 64 as above explained. Y

In order to coordinate the indexing movements of the spindle with thereciprocatlon of the head, pressure fluid may be supplied to thecylinder 61 from the hydraulic circuit of the fluid motor 23. For thispurpose the opposite ends of the cylinder 61 are connected by ducts 'I3and 14 with pressure fluid ducts 15 and 16 extending from the valve V tothe two ports of the motor. The latter ducts are utilized alternately assupply and drain lines for the motor as determined by the setting of thereversing valve V. Thus, when the valve V is set in the position shownin Fig. 4, pressure fluid is supplied to the motor 23 by way of the duct16 and some of this pressure fluid is by-passed to the inner end of thecylinder 61 through the duct 14. The piston 68 is accordingly shifted tothe left to turn the driving element 62 in a clockwise direction. Inthis move- Iii Iii)

ment of the member, the pawl 64 rides over the ratchet teeth 65 so thatno movement is imparted to the spindle.

Upon operation of the valve V to its alternate position, pressure uid issupplied to the motor 23 by way of the duct 15 and a portion of the uidis by-passed through the duct 13 to the outer endof the cylinder 61. Thepiston 68 is thereby shifted to the right to turn the driving element 62in a counterclockwise direction. The pawl 64 now engage-s the ratchetteeth 65 of the driven member 63 which accordingly turns with thedriving member. The movement of the driven member is imparted to thetool spindle through the clutch 6I. tive step imparted to the toolspindle is determined by the length of the stroke of the piston. Thismay be varied as required by means of an adjusting screw 11 threadedinto the side of the casing with its inner end positioned for engagementby the inner end of the piston'rod to limit the forward movement of thesame.

In the operation of the machine for either honing or lapping, it is theusual practice to insert the tool in the work piece in a contractedcondition and thereafter the abrasive elements of the tool are expandedinto engagement with the surface of the work. The expansion andcontraction of such tools are commonly effected in well known manner bysuitable cam means actuated through the medium of a tool-adjusting rod8| which extends from the tool back through the driver and spindle andinto the head.

In the exemplary machine, pressure fluid actuated means is provided forshifting the tool adjusting rod to expand and contract the tool. To thisend, the rod is operatively connected with a piston 82 Working in acylinder 83 mounted in the housing I5 in axial alinementwith the toolspindle. A Vcoiled compression spring 84 encircling the rod normallyacts to hold the piston in the inner end of the cylinder and thus shiftthe adjusting rod to tool contracting position.

For expanding the tool, pressure fluid is introduced into the inner endof the cylinder under control of a valve V2. The piston 82 is therebyshifted outwardly or -to the left as viewed in Fig. 4, thereby movingthe rod 8l t-o tool expanding position.

While the valve V-2 may be operated in any suitable manner, it ispreferred to employ a solenoid for this purpose so'that the expansionand The length of the rotai contraction of the tool may be controlledfrom a convenient remote point. The valve, as herein shown, is equippedwith an operating solenoid S of the usual and well known constructionconnected in a circuit which may conveniently constitute a branch of thecircuit for the electric motor M. The circuit for thesolenoid is adaptedto `be opened and closed by a suitable switch SW. In the exemplarymachine, the switch is arranged to be operated by a push button 85 (Fig.3) mounted on the side of the housing I5 although any other suitableswitch operating means may be employed.

In order to avoid any possibility of driving motoi` when the directionof rotation of the tool and the direction of movement of the head isreversed, means is desirably provided for momentarily relieving thepressure of the tool against the Work at each end of the stroke. In theexemplary machine this is accomplished by momentarily opening thecircuit of the solenoid S which allows the valve V-2 to return to normalposition, thereby disconnecting the tool expanding cylinder from thepressure line extending from the pump P-I. For this purpose two normallyclosed switches SW-l and SW-2 are provided, these switches beingconnected in series with the switch SW in the energizing circuit of thesolenoid S.

As shown in Fig. 3 the switches SW-I and SW--2 are mounted on the base 5for lactuation by a switch engaging member in the form of an arm 88projecting laterally from the head I0. The switches are normally closedand thus complete the circuit for the solenoid when the switch SW isclosed as above described. In operation the switches are positioned forengagement by the arm 88 as the head approaches the respective oppositeends of its stroke, such engagement serving to interrupt the circuit ofthe solenoid and thus momentarily relieving pressure of the tool on thework. Preferably both switches are adjustably secured to the base sothat their position may be readily changed when the machine is set upfor different types of work.

Pressure uid for expanding the honing tool is supplied in the presentinstance by a separate pump P-l driven by the common prime mover of themachine, that is, by the motor M. In this instance the pump is drivinglyconnected to the input shaft 21 of the transmission unit throughthemedium of a gear 86 fast on the shaft so that a constant supply ofpressure iiuid is available for expanding the tool whenever the motor Mis running. If the motor is stopped for any reason, the pressure on thepiston 82 is automatically relieved so that'it can be returned to theinner end of its cylinder by the spring 84 thus enabling the tool tocontract.

It will be apparent from the foregoing that the invention provides ahorizontal honing and lapping machine of novel and improvedconstruction. The tool head of the machine is entirely self-contained,that is, it has included in one unitary structure all of the driving andcontrol instrumentalities required for the operation of the machine.These include the power operated means for reciprocating the head, forrotating the tool spindle continuously, for indexing the tool spindle,and for expanding and contracting the tool. Due to the novel form of thehead, the parts entering into the construction of the machine can belargely standardized for quantity )stalling thel production, thusenabling the machine to be manufactured at relatively low cost.

I claim as my invention:

1. A horizontal honing machine Paving, in combination, an elongatedbase, means at one end of the base for supporting a work piece, ahorizontal guideway at the other end of the base, a self-contained headsupported on the guideway said head having a rotatable spindle adaptedto carry an expansible and contractible honing tool for operating on thework piece, separate power actuated means carried by the head forrotating the spindle," for reciprocating the head and for expanding andcontracting the tool, and a single motor carried by the head operativeto drive all of said power actuated means.

2. A horizontal honing machine having, in combination, an elongatedbase, means at one end of the base for supporting av work piece, ahorizontal guideway at the other end of the base, a self-contained headsupported on the guideway for movement toward and from the work piece,said head having afrotatable spindle adapted to carry a honing tool foroperating on the work piece, separate means carried by the head forrotating the spindle and for reciprocating the head, and a common primemover carried by the head for driving the spindle rotating means and.the head reciprocating means.

3. A horizontal honing machine having, combination, an elongated base,means at one end of the base for supporting a work piece, a horizontalguideway at the other end ci the base, a self-contained head supportedon the guideway for movement toward and from the work piece, said headhaving a rotatable spindle adapted to carry a honing tool for operatingon the work piece, and a single source of power carried by the head forrotating the spindle and for reciprocating the head to traverse the toolrepeatedly from one end of thework piece to the other.

4. In a horizontal honing machine, in ccmbination, a reciprocatory head,a spindle journaled on said head, an elongated tool driver secured atone end to said spindle and carrying at its other end an expansible andcontractible honing tool, pressure fluid operated means on the head forexpanding and contracting the tool, a pump carried by the head forsupplying pressure fluid to said tool expanding and contracting means,pressure uid operated driving means on the head for rotating the spindleand for reciprocating the head, a second pump carried by the head forsupplying pressure fluid to said driving means, and a single motormounted on said head for driving both of said pumps.

5. In a honing machine, in combination, a reciprocatory head, a spindle,iournaled on said head, an elongated tool driver secured at one end tosaid spindle and carrying at its other end an expansible andicontractible honing tool, power actuated means for expandingl the toolinto engagement with the work, a reversible motor for reciprocating thehead and for rotating the spindle, control means for said reversingmotor operative to reverse the direction of rotation of the spindle andto reverse the direction of movement of the head at each end of itsreciprocatory stroke, and control means for said power actuated meansoperative automatically to momentarily relieve the pressure` of the toolon the work upon each reversal of said motor.

6. In a honing machine, in combination, a reciprocatory head, a spindlejournaled on said for movement toward and from the work piece,A

' head, an elongated tool driver 'secured at one end to said spindle andcarrying at its other end an expansible and contractible honing tool,power actuated means for expanding the tool into engagement with thework, power driven means for reciprocating the head. and for rotatingthe spindle, control apparatus for said power driven means operative t`oreverse the direction of rotation of the spindle and to reverse thedirection of movement of the head at each end of its reciprocatorystroke, and other control means operative automatically to momentarilyrelieve the pressure of the tool on the work at each end of said stroke.

'1. In a honing machine, in combination,a reciprocatory head, a spindlejoumaled on said head, an elongated tool driver secured at one end tosaid spindle and carrying at its other end an expansible andcontractible honing tool, pressure fluid actuated means for expandingthe tool into engagement with the work, a valve controlling the supplyof pressure uid to said tool expanding means, .power driven means forreciprocating the head and for rotating the spindle, control apparatusfor said power driven means operative to reverse the direction ofrotation of the spindle and to reverse the direction of movement of thehead at each end of its reciprocatory stroke, and control means for saidvalve actuated by the `head in its reciprocation for operating saidvalve to momentarily relieve the pressure of the tool on the work ateach end of the stroke.

8. In a honing machine, in combination, a reciprocatory head, a spindlejournaled on said head, an elongated tool driver secured at one end tosaid spindle and carrying at its other' end an expansible andcontractible honing tool, power driven means for reciprocating the headand for rotating the spindle, control apparatus for'said power drivenmeans operative to reverse the direction of rotation of the spindle andto reverse'theldirection Vof movement of the head `at e'achfkendof itsreciprocatorystroke, pressure nuid actuated means for expanding the toolinto Vengagement with the work, a valve controlling the supply ofpressure fluid to said tool expanding means, a solenoid associated withsaid valve and operative when energized to set the valve for expandingthe tool, an energizing circuit for said solenoid including a pair ofnormally closed switches, and means carried by said head engageable withsaid switches alternately as the head approaches the respective ends ofits vstroke for momentarily interrupting the circuit of the solenoid torelieve the pressure exerted by the tool on the work.

`9. A horizontal honing machine having, in combination with,an elongatedbase, a self- 10. A horizontal honing machine having, in combinationwith an elongated base, a self-contained head supported forreciprocation on said base, said head comprising a housing, a spindlejournaled at one end ofthe housing and projecting therefrom, a hydraulicvariable speed transmission unit enclosed in said housing, said unithaving power input ,and output shafts, an electric motor coupled to theinput shaft operative to drive the unit, a driving member rotatabyYmounted on the spindle, hydraulically operated means carried byfthehead and supplied with pressure duid from said unit for periodicallyimparting a limited rotative step to said driving,

member, and clutch mechanism enclosed in said housing for connecting thespindle with the output shaft of said unit or with said memberselectivell. A horizontal honingl machine having, in combination with anelongated base, a self-contained' head supported for reciprocation onsaid base, said head comprising a housing, a tool sup- 1 porting spindlejournaled at one end on the housing and projecting therefrom,.a shaftextending transversely of said housing, driving means on said shaftcooperating with means on the base for moving the head relative to thebase, a reversiblepressure fluid motor enclosed in said housing, a geartrain drivingly connecting said motor with said spindle for rotating thespindle, .a second gear train drivingly connecting said motor with saidtransverse shaft for reciprocating the head, a pressure uid pump carriedby the head for supplying pressure fluid to said hydraulic motor, andvalve means controlling the supply of pressure fluid delivered to thehydraulic end on the housing and projecting therefrom, av

contained head supported for reciprocation on' said base, said headcomprising' a housing, a spindle journaled at one end of the housing`and projecting therefrom, a hydraulic variable speed transmission unitenclosed in said housing, said unit having power input and outputshafts, an electric motor coupled tothe input shaft operative to drivethe unit, a gear train drivingly connecting the output shaft of the unitwith said spindle for rotating the spindle, ashaft disposed transverselyof said housing, a pinion on said shaft engageable with a stationaryrack on the base, and a gear'train connectingthe output shaft of saidunit with the pinion shaft for rototing the lsaine to reciprocate thehead.

motor.

, 12. A horizontal honing machine having, in combination with anelongated base. a self-contained head supported for reciprocation on,said' base, a tool supporting spindle journaled at one rotary hydraulicmotor enclosed in said housing, a reciprocatory hydraulic motor alsoenclosed in said housing, clutch mechanism operable to drivingly connectthe spindlewith either motor selectively, a pressure uid pump enclosedin ysaid housing for supplying pressure fluid to both of said motors,and an electric motor'carried by said head for driving said pump. l

13. In a honing mac e. in combination, a reciprocatory head, a to lsupporting spindle journaled on said head, an elongated tool driversecured at one end tothe spindle and carrying at its other end anexpansible and contractible honing tool, poweractuated means` carried byv the head for expanding the tool into engagement with work to beoperated on, a. reversible motor,y

mounted on the head for reciprocating the same to traverse the tool overthe work, control means operativeto reverse the motor at each endofthereciprocatory stroke of the'head, a second motor' carried by said headoperating'simultaneously with said first motor, and 'selectivelyoperable means for drivingly connecting the spindle with either motor,said nrst motoroperating when connected to the spindle to rotate thesame alternately in opposite directions in alternate strokes of the headand said second motor operating when connected to the spindle to rotatethe same in one direction only. I WALTER M. FAIRBAIRN.

